Shift control method of automatic transmission

Abstract

A shift control method of an automatic transmission may include detecting an end point of an inertia section during upshifting, momentarily reducing a hydraulic pressure applied to engagement side frictional elements at the detected end point of the inertia section, increasing the reduced hydraulic pressure with a predetermined gradient until reaching a synchronization point, and momentarily increasing the hydraulic pressure when the synchronization point may be reached.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority to Korean Patent Application No. 10-2011-0059546 filed on Jun. 20, 2011, the entire contents of which is incorporated herein for purposes by this reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to a shift control method of an automatic transmission and, more particularly, to a technique for mitigating shift shock when upshifting.[0004]2. Description of Related Art[0005]The ultimate goal of controlling an automatic transmission is embodying smooth shifting performance. In the conventional technique, hydraulic power transmission apparatuses, such as torque converters, have played an important role in ensuring such smooth shifting performance.[0006]That is, such a conventional torque converter itself absorbs a large proportion of the vibrations or shocks which occurs in a power transmission system due to variations in torque when shiftin...

AI Technical Summary

Benefits of technology

The present invention provides a method to shift gears in an automatic transmission using hydraulic pressure. The method aims to reduce shift shock and make shifting smoother, which improves the overall performance of the vehicle and increases its marketability. It involves detecting the end point of an inertia section during shifting, and then reducing hydraulic pressure to the engagement side friction elements while increasing the pressure with a predetermined gradient until reaching a synchronization point. Once synchronization is reached, the hydraulic pressure is increased again for a moment.

Problems solved by technology

That is, such a conventional torque converter itself absorbs a large proportion of the vibrations or shocks which occurs in a power transmission system due to variations in torque when shifting gears.

However, in a parallel hybrid system or the like in which an electric motor in place of a torque converter is coupled to an input shaft of a transmission by a rigid body, there is no hydraulic clutch which physically absorbs variations in torque which is induced when shifting gears.

Therefore, such variation in torque just causes shift shock, thus markedly deteriorating shifting performance.

In the case of the conventional system provided with the torque converter, slip operation of the torque converter absorbs the majority of such rapid variations in torque, but in the case of a system having no torque converter, rapid variations in torque at the late stage of the shifting process are responsible for deterioration of the shifting performance.

However, in the case of a system having no torque converter, such a shock is just transmitted to the power transmission system as shift shock, thus markedly deteriorating the shifting performance of the vehicle.

Images